Assuming you're wanting a simple iteration and not some type of sort algorithm, this will do the trick.
my $index = 0;
my $input = $ARGV[0] || 'bar';
my @repo = qw (foo bar qux);
$index++ until @repo[$index] eq $input or $index > $#repo; #don't want
+ to loop forever if it's not found

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It's worth noting that in your example, bar is at index 1, not index 2.

Update: Fixed the typo pointed out by dwu

In reply to Re: Finding index of an entry in an Array by jrsimmon
in thread Finding index of an entry in an Array by monkfan

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