To have two \s in your '-delimited string use '\\\\' (two escaped backslaches)

Or else a single escaped backslash and then a single un-escaped backslash:

>perl -wMstrict -le
"my $s1 = 'a\b';
 my $s2 = 'c\\d';
 my $s3 = 'e\\\f';
 my $s4 = 'g\\\\h';
 print $s1, $s2, $s3, $s4;
"
a\bc\de\\fg\\h
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