my $re = join '|', map "($_)", qw[ab ac ad ba bla etc];

for (qw[tab act mad bar blank fetch]) {
    printf "%-6s %-4s %d\n", $_, $+, $#- if /$re/;
}

##</code><code>##

tab    ab   1
act    ac   2
mad    ad   3
bar    ba   4
blank  bla  5
fetch  etc  6