#! perl
use strict;
use warnings;

my %exclude_left  = map { lc $_ => undef } qw( web 2 );
my %exclude_right = map { lc $_ => undef } qw( program call );

my $z = 'Web-developer, perl-program, explicit-element, function-call, 2-x speed.';
my @phrases = split /(\s+)/, $z;

for (@phrases)
{
    #     1 2       3           <-- capture groups
    if (/ ( (\w+) - (\w+) ) /x)
    {
        my ($phrase, $left, $right) = ($1, $2, $3);

        s/$phrase/$right-$left/ unless exists $exclude_left {lc $left } ||
                                       exists $exclude_right{lc $right};
    }
}

print '|', join('', @phrases), "|\n";

##</code><code>##

17:36 >perl 1667_SoPW.pl
|Web-developer, perl-program, element-explicit, function-call, 2-x speed.|

17:36 >