use strict;
my $str = 'eskitirim eski[Verb]-t[Verb+Caus]+[Pos]+Hr[Aor]+YHm[A1sg] : 20.4453125 eski[Verb]-t[Verb+Caus]+[Pos]+Hr[Aor]+Hm[A1sg] : 21.7978515625';
my $regex = qr/(.*?\s.*?)\s.*/p;
my $subst = '\\1';
my $result = $str =~ s/$regex/$subst/r;
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