use strict;
my $str = ' AND op.OP1OPVerfahren > 0
AND p.Testzwecke = 0
AND NOT EXISTS (SELECT DISTINCT 1 FROM ods01.dat_optherapie op2 WHERE op2.patID = p.ID AND op2.revision > op.revision)
UNION ALL
AND op.OP2OPVerfahren > 0
AND p.Testzwecke = 0
AND NOT EXISTS (SELECT DISTINCT 1 FROM ods01.dat_optherapie op2 WHERE op2.patID = p.ID AND op2.revision > op.revision)
UNION ALL';
my $regex = qr/AND op.OP(\d{1,2})(OPVerfahren.*?\))/msp;
my $subst = 'AND op.OP$1$2 \\n GROUP BY OP$1OPVerfahren';
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