Comparing strings case insensitive

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

Replies are listed 'Best First'.
Re: Comparing strings case insensitive by sgifford (Prior) on Sep 12, 2008 at 22:25 UTC
`lc` is much faster, it seems to me, though both are very fast (each of these tests below is for 1m comparisons, so regexp had 150K/s, and lc 1830K/s). `Benchmark: timing 10 iterations of RegExp, lc... RegExp: 66 wallclock secs (66.20 CPU) @ 0.15/s (n=10) lc: 6 wallclock secs ( 5.47 CPU) @ 1.83/s (n=10)` [download] Read more... (895 Bytes) -- sgifford's Web page	[reply] [d/l] [select]
Re: Comparing strings case insensitive by Fletch (Bishop) on Sep 12, 2008 at 21:20 UTC
The first is clearer and less error prone (woe unto you if `$str2` ever contains metacharacters as is), but presuming a recent perl both should be equally speedy. Update: Wow, I must have heard wrong about the re speedups or something; I thought that they supposedly had gotten optimized so fixed strings were on the same order as a vanilla comparison but as the benchmark below shows that's not the case. So yeah, definitely option one. The cake is a lie. The cake is a lie. The cake is a lie.	[reply] [d/l]
Re^2: Comparing strings case insensitive by LesleyB (Friar) on Sep 12, 2008 at 21:26 UTC
So the lower cased string comparison is more robust than the regexp?	[reply]
Re^3: Comparing strings case insensitive by Fletch (Bishop) on Sep 12, 2008 at 21:39 UTC
Yes, because `lc "alligatorz" eq lc "a.z"` will properly compare as unequal, whereas `"alligatorz" =~ /^a.z$/i` incorrectly (for what you're trying to do) will match. That's what I mentioned about robustness, but again with the proper application of `\Q` that wouldn't be an issue. That being said, I'd still use the `lc $x eq lc $y` version vice the `\Q`-ified regexp match as it's more explicit that you're doing a case insensitive comparison between fixed strings. The cake is a lie. The cake is a lie. The cake is a lie.	[reply] [d/l] [select]
Re^3: Comparing strings case insensitive by kyle (Abbot) on Sep 12, 2008 at 21:28 UTC
So the lower cased string comparison is more robust than the regexp? Yes.	[reply]