Two possibilities, with your values appearing to have been chosen specifically for the latter log scaling method?:

##! perl -slw
use strict;

sub genScaler {
    my( $minout, $maxout, $minin, $maxin ) = @_;
    my $outRange = $maxout - $minout;
    my $inRange = $maxin - $minin;
    my $factor = $inRange / $outRange;
    sub {
        my $in = shift;
        return $minout + ( $in / $factor );
    }
}

sub genLogScaler {
    my( $minout, $maxout, $minin, $maxin ) = @_;
    sub {
        my $in = shift;
        $in = 1 if $in < 1;
        return $minout + log( $in );
    }
}

my $fscale = genScaler( 1, 10, 0.1, 8000 );

print "Linear:";
printf "%7.1f -> %.1f\n", $_, $fscale->( $_ ) for 0.1, 1, 10, 100, 800
+, 1000, 4000, 6000, 8000;

print "\nLog:";
my $lscale = genLogScaler( 1, 10, 0.1, 8000 );

printf "%7.1f -> %.1f\n", $_, $lscale->( $_ ) for 0.1, 1, 10, 100, 800
+, 1000, 4000, 6000, 8000;
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Produces:

C:\test>genScalar.pl
Linear:
    0.1 -> 1.0
    1.0 -> 1.0
   10.0 -> 1.0
  100.0 -> 1.1
  800.0 -> 1.9
 1000.0 -> 2.1
 4000.0 -> 5.5
 6000.0 -> 7.8
 8000.0 -> 10.0

Log:
    0.1 -> 1.0
    1.0 -> 1.0
   10.0 -> 3.3
  100.0 -> 5.6
  800.0 -> 7.7
 1000.0 -> 7.9
 4000.0 -> 9.3
 6000.0 -> 9.7
 8000.0 -> 10.0
[download]