system(perl -pib -e "s/CAT/mouse/g" 'D:\tmp\file.txt');

##</code><code>##

system qq|perl -pib -e "s/CAT/mouse/g" 'D:\tmp\file.txt'|;

##</code><code>##

system 'perl', '-pib', '-e', '"s/CAT/mouse/g"', q|'D:\tmp\file.txt'|;

##</code><code>##

C:\temp>perl -lpe "" foo.txt
foo
bar

C:\temp>perl -lpe "" 'foo.txt'
Can't open 'foo.txt': No such file or directory.