$ perl -E ' my @x = qw{ABC DEF BXB}; my ($i, $c) = qw{1 B}; for (@x) { say "$_: ", $i == index($_, $c, $i) ? "YES" : "NO"; say "$_: ", $c eq substr($_, $i, 1) ? "YES" : "NO"; } ' ABC: YES ABC: YES DEF: NO DEF: NO BXB: NO BXB: NO