The split function seems the simplest approach to me:

#! /usr/bin/perl

while(<DATA>) {
   my @field = split " ", $_;
   print "Field 2 => ",$field[1], "\n";
}
__DATA__
ID   SP96_DICDI     STANDARD;      PRT;   600 AA.
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And the output is:

C:\scripts>perl field_split.pl
Field 2 => SP96_DICDI
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