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Re: Explanation of regexps for obtaining POST params

by screamingeagle (Curate)
on Jul 04, 2002 at 20:39 UTC ( #179532=note: print w/ replies, xml ) Need Help??


in reply to Explanation of regexps for obtaining POST params

1) The $FORM variable is a hash which is defined (in your example, should have been defined) before LINE 3 as my %FORM;
2) The tr// operator (i.e. the transliteration operator) is used to search and replace characters
quoting from Perldoc :

tr/SEARCHLIST/REPLACEMENTLIST/cds y/SEARCHLIST/REPLACEMENTLIST/cds Transliterates all occurrences of the characters found in the sear +ch list with the corresponding character in the replacement list. It +returns the number of characters replaced or deleted. If no string is + specified via the =~ or !~ operator, the $_ string is transliterated +. (The string specified with =~ must be a scalar variable, an array e +lement, a hash element, or an assignment to one of those, i.e., an lv +alue.) A character range may be specified with a hyphen, so tr/A-J/0-9/ d +oes the same replacement as tr/ACEGIBDFHJ/0246813579/. For sed devote +es, y is provided as a synonym for tr. If the SEARCHLIST is delimited + by bracketing quotes, the REPLACEMENTLIST has its own pair of quotes +, which may or may not be bracketing quotes, e.g., tr[A-Z][a-z] or tr +(+\-*/)/ABCD/. Note that tr does not do regular expression character classes such + as \d or [:lower:]. The <tr> operator is not equivalent to the tr(1) + utility. If you want to map strings between lower/upper cases, see p +erlfunc/lc and perlfunc/uc, and in general consider using the s opera +tor if you need regular expressions. Note also that the whole range idea is rather unportable between c +haracter sets--and even within character sets they may cause results +you probably didn't expect. A sound principle is to use only ranges t +hat begin from and end at either alphabets of equal case (a-e, A-E), +or digits (0-4). Anything else is unsafe. If in doubt, spell out the +character sets in full. Options: c Complement the SEARCHLIST. d Delete found but unreplaced characters. s Squash duplicate replaced characters.
Line 5 replaces all "+" characters, which in a URL-encoded string, mean spaces.
Line 6 decodes all URL-encoded data to character strings.
The rest of the lines remove all HTML tag-characters , if present.
and finally, the name=>value pair is assigned as a key-value pair to the $FORM hash, so that the rest of the script can refer to the data has $FORM{key}


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