Regular Expressions-Finding info between semicolons

adrianm96 has asked for the wisdom of the Perl Monks concerning the following question:

Hello All, For my input I've got a set of characters each surrounded by semicolons ';'. I'm trying to find one specific letter in the input and take out any information in between the semicolons. It sounds easy but it has stumped me for a day and a half. I've looked into Look-aheads, Look-behinds, anchor points but it seems as if whatever case I use all the criteria isn't met in my regex expression. I could use some help. Here are some examples I've used so far:

/\;(.*?W.*?)\;/

Output:
Letter to find=W
Example Input=;A-B;C-D;E-F;G-H;J-K;L-M;N-P;R-S;T-W;Y-Z;
RegExResult=A-B;C-D;E-F;G-H;J-K;L-M;N-P;R-S;T-W
Issue: Finds the very first semicolon in the whole string
Desired Result: T-W

/\;(.*?L.*?)\;/

Output:
Letter to find=L
Example Input=;A-B-C-D;E-F-G-H;J-K-L-M;N-P-R-S;T-W-Y-Z;
RegExResult=A-B-C-D;E-F-G-H;J-K-L-M
Issue: Finds the very first semicolon in the whole string
Desired Result: J-K-L-M

/\;(.*?B.*?)\;/

Output:
Letter to find=B
Example Input=;A-B;C-D;E-F;G-H;J-K;L-M;N-P;R-S;T-W;Y-Z;
RegExResult=A-B
Issue: No issue, works in this case since its at the beginning of the string
Desired Result: A-B

Comment on Regular Expressions-Finding info between semicolons Select or Download Code

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Re: Regular Expressions-Finding info between semicolons by shmem (Chancellor) on Nov 09, 2016 at 23:21 UTC
Use an inverted character class: `[^;]` instead of `.?` - then `$_ = ';A-B;C-D;E-F;G-H;J-K;L-M;N-P;R-S;T-W;Y-Z;'; print $1, "\n" if /;([^;]W[^;]);/;` [download] yields the desired result. You don't have to escape the semicolon, since it is no meta-character. See perlre and "Bracketed Character Classes" in perlrecharclass. perl -le'print map{pack c,($-++?1:13)+ord}split//,ESEL'	[reply] [d/l] [select]
Re^2: Regular Expressions-Finding info between semicolons by adrianm96 (Novice) on Nov 09, 2016 at 23:44 UTC
This is exactly what I was looking for! I appreciate it! I'll look into what you wrote to fully understand it.	[reply]
Re: Regular Expressions-Finding info between semicolons by choroba (Cardinal) on Nov 09, 2016 at 23:18 UTC
I'd first split the string on semicolons, then you can just grep the string that contains the letter: `#!/usr/bin/perl use warnings; use strict; use feature qw{ say }; for my $tuple ( [ W => ';A-B;C-D;E-F;G-H;J-K;L-M;N-P;R-S;T-W;Y-Z;' ], [ L => ';A-B-C-D;E-F-G-H;J-K-L-M;N-P-R-S;T-W-Y-Z;' ], [ B => ';A-B;C-D;E-F;G-H;J-K;L-M;N-P;R-S;T-W;Y-Z;' ], [ A => ';A-B-C;D-E-F-G-H-J-K-L;M-N-P-R-S-T;W-Y-Z;' ], [ Z => ';A-B-C;D-E-F-G-H-J-K-L;M-N-P-R-S-T;W-Y-Z;' ], ) { my ($letter, $string) = @$tuple; say "$letter: ", grep index($_, $letter) != -1, split /;/, $string +; }` [download] ($q=q:Sq=~/;[c](.)(.)/;chr(-\|\|-\|5+lengthSq)`"S\|oS2"`map{chr \|+ord }map{substrSq`S_+\|`\|}3E\|-\|`7**2-3:)=~y+S\|`+$1,++print+eval$q,q,a, [download]	[reply] [d/l] [select]
Re: Regular Expressions-Finding info between semicolons by Paladin (Vicar) on Nov 09, 2016 at 23:25 UTC
This is a fairly common issue I see with Regex. People use `.` in their regexen when that's not what they actually mean. In your example you have: `/\;(.?L.?)\;/`. You are looking for a L surrounded by a bunch of stuff that isn't semicolons, but `.` means "everything", not "everything except semicolons". If you want to say "everything except semicolons" in the regex, then say that: `/\;([^;]?L[^;]?)\;/` `[~]$ perl -le '$_ = ";A-B-C-D;E-F-G-H;J-K-L-M;N-P-R-S;T-W-Y-Z;"; /\;([ +^;]?L[^;]?)\;/; print $1;' J-K-L-M` [download] tl;dr: Don't use `.` if you don't mean `.`	[reply] [d/l] [select]
Re^2: Regular Expressions-Finding info between semicolons by adrianm96 (Novice) on Nov 09, 2016 at 23:42 UTC
Thanks for your help! Yeah I saw what was happening, I was just having trouble translating what I wanted into code to match the pattern. Thanks again!	[reply]
Re: Regular Expressions-Finding info between semicolons by tybalt89 (Monsignor) on Nov 09, 2016 at 23:24 UTC
`#!/usr/bin/perl # http://perlmonks.org/?node_id=1175635 use strict; use warnings; my @testcases = ( [ 'W', ';A-B;C-D;E-F;G-H;J-K;L-M;N-P;R-S;T-W;Y-Z;' ], [ 'L', ';A-B-C-D;E-F-G-H;J-K-L-M;N-P-R-S;T-W-Y-Z;' ], [ 'B', ';A-B;C-D;E-F;G-H;J-K;L-M;N-P;R-S;T-W;Y-Z;' ], ); for ( @testcases ) { my ( $letter, $string ) = @$_; $string =~ /.;(.?$letter.*?);/ and print "$letter $1\n"; }` [download]	[reply] [d/l]


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