use strict;
my $str = 'Aance petty cash - Site 21/03/2019||Y|17-OCT-19|17-OCT-19|17-OCT-19|KMADRZYK|MANUAL W|SAKM18OCT19|S|158 \\\\fpp01\\Finance\\Finance\\AP_PROCESSING\\1_MEN|SAR
Aance petty cash - Site 21/03/2019||Y|17-OCT-19|17-OCT-19|17-OCT-19|KMADRZYK|MANUAL W|SAKM18OCT19|S|\\krv|SAR
Aance petty cash - Site 21/03/2019||Y|17-OCT-19|17-OCT-19|17-OCT-19|KMADRZYK|MANUAL W|SAKM18OCT19|M|sd01\\Finance\\Finance\\AP_PROCESSING\\1_MEN |SAR
Aance petty cash - Site 21/03/2019||Y|17-OCT-19|17-OCT-19|17-OCT-19|KMADRZYK|MANUAL W|SAKM18OCT19|M|159\\fpp01\\Finance\\Finance\\AP_PROCESSING\\1_MEN |SAR
Studying and updating dmmmy ||Y|17-OCT-19|18-OCT-19|18-OCT-19|KMADRZYK|MANUAL W|SAKM18OCT19|T|160 -|SAR
Johannes Märkl Monatsrechnung ----||N|17-OCT-19|18-OCT-19|18-OCT-19|KMADRZYK|MANUAL W|SAKM18OCT19|S||SAR';
my $regex = qr`[\\\/\/]`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