It would operate the same as this, but without the need to re-state the loop variable 3 times:

#! perl -slw
use strict;

my @a = qw [a b c];
for( $a[7] = 1; $a[ 7 ] <= 5; ++$a[7] ) {
    print $a[ 7 ];
}
print 0 + @a;
print "@a";

__END__
C:\test>junk2.pl
1
2
3
4
5
8
Use of uninitialized value in join or string at C:\test\junk2.pl line 
+10.
Use of uninitialized value in join or string at C:\test\junk2.pl line 
+10.
Use of uninitialized value in join or string at C:\test\junk2.pl line 
+10.
Use of uninitialized value in join or string at C:\test\junk2.pl line 
+10.
a b c     6
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