Selective Case sensitivity

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

I am looking to create a single regex statement that is generally case insensitive, but, within the statement, demands a certain case. For example, I want to match a general pattern like this:

A) Title of paragraph

But dont want to match this:

a) Title of paragraph

The trouble is, the "title of paragraph" portion needs to be case insensitive, so, I want the statement to also match this

A) TiTLE of PARagraPh

but not this:

a) TiTLE of PARagraPh

Is there any way to accomplish this in a single regex statement? If I turn the "i" pattern modifier on, is there any way to turn it off for a small portion of the regular expression (the "A)") portion? Thanks.

Comment on Selective Case sensitivity

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Re: Selective Case sensitivity by toolic (Bishop) on Feb 18, 2012 at 19:59 UTC
Extended Patterns `use warnings; use strict; while (<DATA>) { chomp; if (/A\) (?i:Title)/) { print "$_: matches\n"; } else { print "$_: does not match\n"; } } __DATA__ A) title a) title A) TItlE` [download] prints: `A) title: matches a) title: does not match A) TItlE: matches` [download]	[reply] [d/l] [select]
Re: Selective Case sensitivity by davido (Cardinal) on Feb 18, 2012 at 19:59 UTC
Yes, you can do that. Here's a simple example: `my @strings = ( 'abBbBBbb', 'AbBbBBbb', ); foreach my $string ( @strings ) { if( $string =~ m/(?-i:a)b+/i ) { print "$string matched.\n"; } else { print "$string didn't match\n"; }` [download] In particular, the `(?flags:PATTERN)` construct as documented in perlre is what you're after. To turn on case sensitivity for a submatch where it's off in a broader scope you would say `(?i:PATTERN)`, and to turn it off for a submatch (where it's on in a broader scope) you would say `(?-i:PATTERN)`. Dave	[reply] [d/l] [select]
Re: Selective Case sensitivity by LonelyPilgrim (Beadle) on Feb 18, 2012 at 19:57 UTC
How about this? `/[A-Z]\) (?i:title of paragraph)/` That should make the string with the parens case-insensitive, while leaving the stuff outside case sensitive.	[reply] [d/l]