my $eqn='$profit=$sales-$cogs';
my @wrds = split /(=)|(-)/, $eqn;  
#gives profit,=,,$sales,,-,$cogs
my $wrds_str=join(",",@wrds);
$wrds_str =~ s/,,/,/g;
@wrds = split /,/, $wrds_str; 
print join ",",@wrds;