I tried to test this and it seems as though your regular expression is working fine. I had to make some small changes to test it and removed the single quotes on the second line ('$gpa $gpa_key') and replaced it with ($gpa_ret = "gpa: $gpa_key"). Otherwise, the value would not interpolate for the regex.

my $gpa_key = "azxinetgw.EXECFILE_DIR.azxinetgw='/usr/local/instinet/R
+TS/etc/local/azxfiles'";
    my $gpa_ret = "gpa: $gpa_key";
    warn $gpa_ret;
    print "gpakey: $gpa_key\n";
    #print "gparet: $gpa_ret\n";
    if (  $gpa_ret =~ /[^=]+[=][']([^']+)[']/ ) { 
            my $assigned_dir = $1 ;
            print "$assigned_dir\n";} 
    else { die "couldn't determine assigned directory for    $gpa_key"
+ 
    }
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By making this change, we are now passing the string instead of the literal name of the variable. You were actually testing the regex conditions on `$gpa $gpa_key` instead of the string value. The output from my modified version is:

gpa: azxinetgw.EXECFILE_DIR.azxinetgw='/usr/local/instinet/RTS/etc/loc
+al/azxfiles' at D:\DATA_TO_MIGRATE\dbexamples\ex\gpa.pl line 7
.
gpakey: azxinetgw.EXECFILE_DIR.azxinetgw='/usr/local/instinet/RTS/etc/
+local/azxfiles'
/usr/local/instinet/RTS/etc/local/azxfiles
[download]

Mick