my %sub = {
 ">" => "\t\t++k;\n",
 "+" => "\t\t++*k;\n",
 ... # fill as needed
 }
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The hash initialization statement above should use parentheses and not curlies:
    my %sub = ( ... );

s/(.)/$sub{$1}/ge

Also note that the  /e modifier is not needed in this substitution (although it does no harm except to burn some time) because  $sub{$1} is already a scalar that can be interpolated into a string.