use strict;
my $str = 'TREE(abc/x73/APPLE) DEST(MYFILE.FILE1A)
TREE(abc/x74/APPLE) DEST(MYFILE88.FILE1A)
TREE(abc/x100/APPLE) DEST(MYFILE100.FILE1B)
TREE(abc/x61/APPLE) DEST(MYFILE1000.FILE1A)';
my $regex = qr/(\([^()]*\)[[:blank:]][[:blank:]]*)[^()]*\([^()]*\.([^()]*)\)/mp;
my $subst = '$1$2';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html