String::Glob::Permute - Expand {foo,bar,baz}[2-4] style string globs


    use String::Glob::Permute qw( string_glob_permute );

    my $pattern = "host{foo,bar,baz}[2-4]";

    for my $host (string_glob_permute( $pattern )) {
        print "$host\n";

      # hostfoo2
      # hostbar2
      # hostbaz2
      # hostfoo3
      # hostbar3
      # hostbaz3
      # hostfoo4
      # hostbar4
      # hostbaz4


The string_glob_permute() function provided by this module expands glob-like notations in text strings and returns all possible permutations.

For example, to run a script on hosts host1, host2, and host3, you might write

    @hosts = string_glob_permute( "host[1-3]" );

and get a list of hosts back: ("host1", "host2", "host3").

Ranges with gaps are also supported, just separate the blocks by commas:

    @hosts = string_glob_permute( "host[1-3,5,9]" );

will return ("host1", "host2", "host3", "host5", "host9").

And, finally, using curly brackets and comma-separated lists of strings, as in

    @hosts = string_glob_permute( "host{dev,stag,prod}" );

you'll get permutations with each of the alternatives back: ("hostdev", "hoststag", "hostprod") back.

All of the above can be combined, so

    my @hosts = string_glob_permute( "host{dev,stag}[3-4]" );

will result in the permutation ("hostdev3", "hoststag3", "hostdev4", "hoststag4").

The patterns allow numerical ranges only [1-3], no string ranges like [a-z]. Pattern must not contain blanks.

The function returns a list of string permutations on success and undef in case of an error. A warning is also issued if the pattern cannot be recognized.

Zero padding

An expression like

    @hosts = string_glob_permute( "host[8-9,10]" );
      # ("host8", "host9", "host10")

will expand to ("host8", "host9", "host10"), featuring no zero-padding to create equal-length entries. If you want ("host08", "host09", "host10"), instead, pad all integers in the range expression accordingly:

    @hosts = string_glob_permute( "host[08-09,10]" );
      # ("host08", "host09", "host10")

Note on Perl's internal Glob Permutations

Note that there's a little-known feature within Perl itself that does something similar, for example

    print "$_\n" for < foo{bar,baz} >;

will print


if there is no file in the current directory that matches that pattern. String::Glob::Permute, on the other hand, expands irrespective of matching files, by simply always returning all possible permutations. It's also worth noting that Perl's internal Glob Permutation does not support String::Glob::Permute's [m,n] or [m-n] syntax.


Copyright (c) 2008 Yahoo! Inc. All rights reserved. The copyrights to the contents of this file are licensed under the Perl Artistic License (ver. 15 Aug 1997).


Algorithm, Code: Rick Reed, Ryan Hamilton, Greg Olszewski. Module: 2008, Mike Schilli <>