Can't reproduce it, though I'm also using Linux and bash.  With your sample code I'm getting something like:

$ ./724323.pl &
[2] 10620
[download]

(no further output)

$ ps x | grep 724323
10620 pts/1    T      0:00 /usr/bin/perl ./724323.pl
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(the 'T' indicates that the script has been stopped)

$ fg
./724323.pl
# Start script

    -> Waiting 2 seconds

    -> Waiting 2 seconds
# Exiting ..
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(after foregrounding it, output continues normally)