foreach $line ( @fileData ) {
    $linenumber++;
    if ( $line =~ m/^1$/) {
        print "$linenumber\n";
    }
}

##</code><code>##

for ( @fileData ) {
    $linenumber++;
    if ( m/^1$/ ) {
        print "$linenumber\n";
    }
}

##</code><code>##

$l++,/^1$/&&print$l.$/for@f;