How can I find the first position of a substring case-insensitively?

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

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Re: How can I find the first position of a substring case-insensitively? by eg (Friar) on Dec 02, 2000 at 11:55 UTC
The easiest thing to do would be to use `lc` on `$mystr` like so: my $index = index( lc( $mystr ), "a" ); Edited by Russ: Combined posts by ambiguous, tektsu, kilinrax, ariels, and tenatious into one	[reply]
Re: How can I find the first position of a substring case-insensitively? by ambrus (Abbot) on Oct 01, 2003 at 12:43 UTC
You could use regexps, like this: `$needle = "a"; $haystack =~ /\Q$needle\E/i; $index = $-[0];` [download] this works even if `$needle` has regexp-metacharacters in it. But `@-` exists only in newer perls (from 5.6.1 I think). In perl 5.005 you could use something like `$needle = "a"; $haystack =~ /\Q$needle\E/i; $index = pos($haystack)-length($needle);` [download] or $needle = "a"; $haystack =~ /\Q$needle\E/i; $index = length($`); [download] but note that $` makes perl slower. Whitespace added by tye	[reply] [d/l] [select]
Re: How can I find the first position of a string within a string by zejames (Hermit) on Dec 01, 2000 at 18:25 UTC
I think you could simply do this : `my $position = index(lc($mystr),"a");` [download] You first "lowercase" the string, and then look for your substring into it. HTH James	[reply] [d/l]
Re: How can I find the first position of a string within a string by chipmunk (Parson) on Dec 01, 2000 at 19:46 UTC
How about a regex? `if ($mystr =~ /(?=a)/gi) { $position = pos($mystr); }` [download] I use a positive lookahead assertion so that pos() will correspond to the start of the match, rather than the end.	[reply] [d/l]
Re: How can I find the first position of a substring case-insensitively? by ambiguous (Novice) on Dec 03, 2000 at 16:54 UTC
As far as I know you cannot make index() case insensitive. I think the simpliest thing to do is to make you string case insensitive. Ex. `my $lcstr = lc $mystr; my $ind = index($lcstr,"a");` [download] This way "a" matches the first instance of "A" or "a" in the original $mystr. Hope that helps. Originally posted as a Categorized Answer.	[reply] [d/l]
Re: How can I find the first position of a substring case-insensitively? by Anonymous Monk on Dec 05, 2000 at 09:01 UTC
index(lc $mystr,"a") Originally posted as a Categorized Answer.	[reply]
Re: How can I find the first position of a substring case-insensitively? by tektsu (Acolyte) on Dec 06, 2000 at 23:44 UTC
How about index(lc $mystr,"a")?<br I'm not sure how efficient it is, but it does work... Originally posted as a Categorized Answer.	[reply]
Re: How can I find the first position of a substring case-insensitively? by tenatious (Beadle) on Dec 05, 2000 at 23:19 UTC
`$b = index(lc($mystr),"a");` [download]	[reply] [d/l]
Re: Answer: How can I find the first position of a substring case-insensitively? by cogent (Monk) on Dec 06, 2000 at 00:49 UTC
It's kind of a pain in the butt, but here's one way: `my $haystack = "foobar"; my $needle = "Bar"; $haystack =~ /($needle)/gi; print ((pos $haystack) - (length $needle));` [download]	[reply] [d/l]
Re: How can I find the first position of a substring case-insensitively? by kilinrax (Deacon) on Dec 01, 2000 at 21:20 UTC
You could just use '`lc`' to test for 'a' in the lowercased version of the string (which would effectively be the same thing). `index(lc($mystr),'a')` [download] Originally posted as a Categorized Answer.	[reply] [d/l]
Re: How can I find the first position of a substring case-insensitively? by ariels (Curate) on Dec 03, 2000 at 14:35 UTC
`index(lc($mystr), "a");`. If you want to look for `$mysubstr` instead of for `"a"`, and you don't know that it's all lowercase, you'll need to apply `lc` to that as well, of course. Originally posted as a Categorized Answer.	[reply] [d/l] [select]
Re: How can I find the first position of a substring case-insensitively? by ariels (Curate) on Dec 03, 2000 at 14:35 UTC
`index(lc($mystr), "a");. If you want to look for $mysubstr instead of for "a", and you don't know that it's all lowercase, you'll need to apply lc to that as well, of course. Originally posted as a Categorized Answer.`	[reply] [d/l] [select]
Re: How can I find the first position of a substring case-insensitively? by Anonymous Monk on Dec 10, 2000 at 03:29 UTC
index(lc $mystr,"a") Originally posted as a Categorized Answer.	[reply]
Re: How can I find the first position of a substring case-insensitively? by ambrus (Abbot) on Oct 01, 2003 at 12:55 UTC
You could use regexps, like this: `$needle="a"; $haystack=~/\Q$needle/i; $index=$-[0];` this works even if `$needle` has regexp-metacharacters in it. But `@-` exists only in newer perls (from 5.6.1 I think). In perl 5.005 you could use something like `$needle="a"; $haystack=~/\Q$needle/i; $index= pos($haystack)-length($needle)` or $needle="a"; $haystack=~/\Q$needle/i; $index= length($`); but note that $` makes perl slower. Originally posted as a Categorized Answer.	[reply] [d/l] [select]
Re: How can I find the first position of a substring case-insensitively? by ambrus (Abbot) on Oct 01, 2003 at 12:56 UTC
You could use regexps, like this: `$needle="a"; $haystack=~/\Q$needle/i; $index=$-[0];` this works even if `$needle` has regexp-metacharacters in it. But `@-` exists only in newer perls (from 5.6.1 I think). In perl 5.005 you could use something like `$needle="a"; $haystack=~/\Q$needle/i; $index= pos($haystack)-length($needle)` or $needle="a"; $haystack=~/\Q$needle/i; $index= length($`); but note that $` makes perl slower. Originally posted as a Categorized Answer.	[reply] [d/l] [select]