use strict;
my $str = 'Doc20191001119049_fotocontargasx_3962122_943000.jpg
Doc201810011052053_fotoAssicurazioneCartaceo_3962128_943000.jpg
Doc201910011214020_fotoesterna_ant_396024_947112.jpg
Doc201710071149010_foto_TargaMid_4007396_95010.jpg';
my $regex = qr/^[^_]*_|_\d+_\d+\.[^.]*$/mp;
my $subst = '';
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