quantifiers with digits (\d{1|2} doesn't do what I expect)

efoss has asked for the wisdom of the Perl Monks concerning the following question:

I have a bunch of file names in the array called "@array". I want to pull out those files that start with "KL" and then either 1 or 2 digits and then an underscore, and I want to push those files onto the array called "@files". This is how I tried to do this:

foreach $file (@array) {
    if ($file =~ /^KL\d{1|2}_/) {
        push (@files, $file);
        print "$file\n";
    }
}
[download]

This doesn't work. However, the following works, but only because all the files in "@array" have either 1 or 2 digits following the initial "KL". If there had been a file name in @array like "KL123_rest.txt" that I didn't want to push onto the array "@files", then my code wouldn't have worked.

foreach $file (@array) {
    if ($file =~ /^KL\d+_/) {
        push (@files, $file);
        print "$file\n";
    }
}
[download]

How do I correctly quantify \d in this situation? Thanks. Eric

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Re: quantifiers with digits (\d{1\|2} doesn't do what I expect) by davido (Cardinal) on Aug 21, 2012 at 01:56 UTC
The syntax for brace quantifiers is to use a comma: `{0,2} # Max of 2 {1,3} # One to three {1,} # One or more {2} # Exactly two {1,2} # One to two.` [download] There is no concept of alternation within quantifier braces. Dave	[reply] [d/l]
Re^2: quantifiers with digits (\d{1\|2} doesn't do what I expect) by efoss (Acolyte) on Aug 21, 2012 at 16:10 UTC
Thanks so much, Dave. Eric	[reply]
Re: quantifiers with digits (\d{1\|2} doesn't do what I expect) by BillKSmith (Monsignor) on Aug 21, 2012 at 02:55 UTC
Use `grep` `use strict; use warnings; my @array = qw(KL1_something.txt KL12_anything.dat KL123_rest.txt); my @file = grep /^KL\d{1,2}_/, @array; print "@file\n";` [download] Bill	[reply] [d/l] [select]
Re: quantifiers with digits (\d{1\|2} doesn't do what I expect) by ricDeez (Scribe) on Aug 21, 2012 at 07:56 UTC
How about this as an alternative? `if ($file =~ /^KL\d\d?_/) {...}`	[reply] [d/l]