How can I make hash key lookup case-insensitive?

Question

Evidently hash keys are compared in a case-sensitive manner.

$ perl -e '%hash = ( FOO => 1 ); printf "%s\n", ( exists $hash{foo} ) ? "Yes" : "No";'
No

$ perl -e '%hash = ( FOO => 1 ); printf "%s\n", ( exists $hash{FOO} ) ? "Yes" : "No";'
Yes

Is there a setting to change that for the current script?

Thanks.

Answer 1

The hash of a string and the same string with the case changed are not equal. So you can't do what you want, short of calling "uc" on every hash key before you create it AND before you use it.

Answer 2

You will have to use a tied hash. For example Hash::Case::Preserve.

Answer 3

my %hash = (FOO => 1);
my $key = 'fOo'; # or 'foo' for that matter

my %lookup = map {(lc $_, $hash{$_})} keys %hash;
printf "%s\n", ( exists $hash{(lc $key)} ) ? "Yes" : "No";