Additionally to what has been said already:

• you might like to quote the link that you give to curl, e.g. my $curlc = "curl $curla '$link'";
• you might like to redirect the error-stream of curl to /dev/null or to STDIN (2>&1), but be aware that curl can print progress information to STDERR
• A timout of 10.000s is quite high.
• Update: If you want to check accessibility and document-existence only, it would be sufficient to download the header information only (curl switch: --head), not the whole file. Then check for /HTTP\S+\s+(\d+)\s+/ and $1 eq 200 for an existing file.