johngg has answered your "meta-question" (which seems to be "how do I stop processing a file when I find what I'm looking for"), but if you really want to move the file read pointer to the beginning or end of a file then you can use the seek function.

use Fcntl qw(:seek)# load symbolic constants

seek FILEHANDLE, 0, SEEK_SET; # start of file
seek FILEHANDLE, 0, SEEK_END; # end of file
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