@foo = qw( a b c d e f g h i j k l m n o p q r s t u v w y z );

my @feh = sort { rand(1) >= .5 } @foo;  # randomly sort

my $upper = int( scalar(@feh) * .75 );  # upper index to get 75% of records
print join (",", @feh[ 0 .. $upper]); 

#Example output:
#C:\>perl randsort.pl
#q,r,p,j,o,d,a,b,c,g,e,h,f,i,l,k,m,n,s
#C:\>perl randsort.pl
#t,g,r,s,q,o,p,b,h,e,f,a,c,d,m,n,l,k,i