use strict;
use warnings;

while ( my $line = <DATA> ) {
    next unless $line =~ /\band\b/;
    chomp $line;
    my @words = split /\s+/, $line;
    my $location = 0;
    my @locations;
    foreach ( @words ) {
        $location++;
        push @locations, $location if m/\band\b/;
    }
    local $" = ", ";
    print "Line $.: 'and' appears as word @locations.\n";
}

__DATA__
This is a test and a test and a test.