B::Concise - Walk Perl syntax tree, printing concise info about ops
perl -MO=Concise[,OPTIONS] foo.plThis compiler backend prints the internal OPs of a Perl program's syntax tree in one of several space-efficient text formats suitable for debugging the inner workings of perl or other compiler backends. It can print OPs in the order they appear in the OP tree, in the order they will execute, or in a text approximation to their tree structure, and the format of the information displyed is customizable. Its function is similar to that of perl's -Dx debugging flag or the B::Terse module, but it is more sophisticated and flexible.
Arguments that don't start with a hyphen are taken to be the names of subroutines to print the OPs of; if no such functions are specified, the main body of the program (outside any subroutines, and not including use'd or require'd files) is printed.
Print OPs in the order they appear in the OP tree (a preorder traversal, starting at the root). The indentation of each OP shows its level in the tree. This mode is the default, so the flag is included simply for completeness.
Print OPs in the order they would normally execute (for the majority of constructs this is a postorder traversal of the tree, ending at the root). In most cases the OP that usually follows a given OP will appear directly below it; alternate paths are shown by indentation. In cases like loops when control jumps out of a linear path, a 'goto' line is generated.
Print OPs in a text approximation of a tree, with the root of the tree at the left and 'left-to-right' order of children transformed into 'top-to-bottom'. Because this mode grows both to the right and down, it isn't suitable for large programs (unless you have a very wide terminal).
Use a tree format in which the minimum amount of space is used for the lines connecting nodes (one character in most cases). This squeezes out a few precious columns of screen real estate.
Use a tree format that uses longer edges to separate OP nodes. This format tends to look better than the compact one, especially in ASCII, and is the default.
Use tree connecting characters drawn from the VT100 line-drawing set. This looks better if your terminal supports it.
Draw the tree with standard ASCII characters like + and |. These don't look as clean as the VT100 characters, but they'll work with almost any terminal (or the horizontal scrolling mode of less(1)) and are suitable for text documentation or email. This is the default.
Include the main program in the output, even if subroutines were also specified.
Print OP sequence numbers in base n. If n is greater than 10, the digit for 11 will be 'a', and so on. If n is greater than 36, the digit for 37 will be 'A', and so on until 62. Values greater than 62 are not currently supported. The default is 36.
Print sequence numbers with the most significant digit first. This is the usual convention for Arabic numerals, and the default.
Print seqence numbers with the least significant digit first.
Use the author's favorite set of formatting conventions. This is the default, of course.
Use formatting conventions that emulate the ouput of B::Terse. The basic mode is almost indistinguishable from the real B::Terse, and the exec mode looks very similar, but is in a more logical order and lacks curly brackets. B::Terse doesn't have a tree mode, so the tree mode is only vaguely reminiscient of B::Terse.
Use formatting conventions in which the name of each OP, rather than being written out in full, is represented by a one- or two-character abbreviation. This is mainly a joke.
Use formatting conventions reminiscient of B::Debug; these aren't very concise at all.
Use formatting conventions read from the environment variables B_CONCISE_FORMAT, B_CONCISE_GOTO_FORMAT, and B_CONCISE_TREE_FORMAT.
For each general style ('concise', 'terse', 'linenoise', etc.) there are three specifications: one of how OPs should appear in the basic or exec modes, one of how 'goto' lines should appear (these occur in the exec mode only), and one of how nodes should appear in tree mode. Each has the same format, described below. Any text that doesn't match a special pattern is copied verbatim.
Generates exec_text in exec mode, or basic_text in basic mode.
Generates one copy of text for each indentation level.
Generates one fewer copies of text1 than the indentation level, followed by one copy of text2 if the indentation level is more than 0.
If the value of var is true (not empty or zero), generates the value of var surrounded by text1 and Text2, otherwise nothing.
Generates the value of the variable var.
Generates the value of var, left jutified to fill N spaces.
Any number of tildes and surrounding whitespace will be collapsed to a single space.
The following variables are recognized: