$str = '004asdfsa'; #string starting with zero and followed by numbers

$str =~ s/^0+(?=\d)//;

print $str;

Output:
--------
4asdfsa

##</code><code>##

$str = 'a004asdfsa'; #not starting with zero

$str =~ s/^0+(?=\d)//;

print $str;

Output:
--------
a004asdfsa

##</code><code>##

$str = '0a4sdfsa'; #no number followed by zero

$str =~ s/^0+(?=\d)// ;

print $str;

Output:
--------
0a4sdfsa