$val=$val+0;			# Sum
$val=eval "$val";		# Eval
$val=sprintf("%f", $val);	# Sprintf
	# Call your original technique "Regex"

##</code><code>##

Sum("1.25e-5")           gives  '1.25e-05'
Regex("1.25e-5")                '1.25e-05'
Eval("1.25e-5")                 '1.25e-05'
Sum("1.25e-3")                  0.00125
Regex("1.25e-3")                0.00125
Eval("1.25e-3")                 0.00125

##</code><code>##

Sprintf("1.25e-5")              0.000013
Sprintf("1.25e-3")              0.001250
Sprintf("1.25e-7")              0.000000

##</code><code>##

sprintf("%.10f", $val)          0.0012500000

##</code><code>##

Benchmark: timing 100000 iterations of Eval, Regex, Sprintf, SprintfSubst, Sum...
      Eval: 20 wallclock secs (19.58 usr +  0.00 sys = 19.58 CPU)
     Regex:  9 wallclock secs ( 9.97 usr +  0.00 sys =  9.97 CPU)
   Sprintf:  7 wallclock secs ( 6.22 usr +  0.00 sys =  6.22 CPU)
SprintfSubst:  8 wallclock secs ( 8.74 usr +  0.00 sys =  8.74 CPU)
       Sum:  4 wallclock secs ( 3.52 usr +  0.00 sys =  3.52 CPU)

##</code><code>##

#!/usr/bin/perl

use Benchmark;

sub Regex {
  my $val=shift;
  $val =~ s/([\.\d]+)e([-+]?\d+)/$1*10**$2/egi;
  return $val;
}

sub Eval {
  my $val=shift;
  $val=eval " $val ";
  return $val;
}

sub Sum {
  my $val=shift;
  $val=$val+0;
  return $val;
}

sub Sprintf {
  my $val=shift;
  $val=sprintf("%f",$val);
  return $val;
}

sub SprintfSubst {
  my $val=shift;
  $val=sprintf("%.10f", $val);
  $val=~s/0*$//;
  return $val;
}

timethese(100000, { Regex => sub { Regex("1.25e-3") },
                   Eval =>  sub { Eval("1.25e-3") },
                   Sum => sub { Sum("1.25e-3") },
                   Sprintf => sub { Sprintf("1.25e-3") },
                   SprintfSubst => sub { SprintfSubst("1.25e-3") },
                  });