grinder already mentioned a number of issues, but there are more:

• Use of numbered scalars instead of arrays makes for very repetitive code.
• Speaking of repetition, why are %slash and %decimal built by hand?!?
• None of your variables are scoped. Adding use strict; will show those errors.
• The code in the BEGIN block doesn't belong in a BEGIN block.
• Meet join, the converse of split.
• Meet $., line counter.
• The use of clear is not only unnecessary, it's not portable.
• $_ =~ s/.../.../g; can be written as s/.../.../g;.