# 读写文件.
#/usr/bin/perl -w
use 5.010;        # Use 'say'.

# Read from file.
open F, "<data.txt"
    or die "fail: open()";
my @arr = <F>;    # Read all data to array.
close F;

# Write to file.
open F, ">res.txt"    # Use ">>" if you want to append at end.
    or die "fail: open()";
while (@arr) {
print F ($_."\n");    # Write to file.
}
close F;

# 将单词首字母大写, 其它字母小写
$_="walfud ranisic durk" ;
s/(\b\w+\b)/\u\L$1\E/g ;

print ;
 

# 批量改名
foreachmy$name (glob"*.old") {
my$newName=$name ;
$newName=~ s/\.old$/\.new/ ;

if (-e $newName) {
warn"can't rename '$name' to '$newName': $newName exists"."\n" ;
    } else {
rename$name,$newName
            or warn"rename '$name' to '$newName' failed: $!"."\n" ;
    }
}

# 将长整数每三位以 ',' 分隔
my$number="1234567890123" ;
1while$number=~ s/^(-?\d+)(\d\d\d)/$1,$2/ ;

print$number ;