use strict;
use warnings;
use List::Util qw/first/;


my @array=(1,2);

my $i1 = first { $array[$_] == 1 } (0..$#array);
my $i2 = first { $array[$_] == 2 } (0..$#array);
my $i3 = first { $array[$_] == 3 } (0..$#array);

print "<$i1> <$i2> <$i3>\n";

##</code><code>##

Use of uninitialized value $i3 in concatenation (.) or string at d:/tmp/first.pl line 13.
<0> <1> <>