The order of your arguments is wrong, it should be
strftime(fmt, sec, min, hour, mday, mon, year)
where mon begins at zero and year is since 1900.

my $datetimestring = "5/4/13 16:09";
my ($month,$day,$year,$hour,$min) = split /\D/,$datetimestring;
my $str =  strftime("%b %d %Y %H:%M:%S", 0,$min,$hour,$day,$month-1,$y
+ear+100);
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