Perl's **ellipsis statement** (`...`) acts as a placeholder for code not yet implemented. 

Although Perl parses the ellipsis statement without issue, the `Unimplemented` exception is thrown if an attempt is made to execute the code.

<h2>Syntax</h2>

Syntactically, the ellipsis statement is represented using the `...;` operator. It can be used in place of any complete statement. The semi-colon (`;`) can be omitted if the ellipses statement is immediately followed by a closing brace ( `}` ).

The commands below show the appropriate syntax for invoking the ellipsis statement:

```Perl
## Method 1
sub thisFunc{ ... }

## Method 2
sub thisFunc{ ...; }
``` 

<h3>Examples</h3>

The code below shows different examples of how the ellipsis statement can be used in Perl:


#!/usr/bin/perl

# unimplemented function
sub funcOne { ... }

# function with two unimplemented statements
sub funcTwo {
    print "Inside funcTwo!\n";
    ...;
    { ... }
}

# placeholder for eval expression
eval { ... };

# catch exception thrown by subroutines
eval { funcOne() };
if ($@ =~ /^Unimplemented/) {
    print "Unimplemented Function.\n";
}

eval { funcTwo() };
if ($@ =~ /^Unimplemented/) {
    print "Unimplemented Function.\n";
}


<h3>Explanation</h3>

The code above shows $3$ different ways the `...` operator can be used as a placeholder for unimplemented statements.

The code defines two subroutines: `funcOne` and `funcTwo`. The `funcOne` subroutine is completely unimplemented with the `...` statement as a placeholder for the missing statements. The `funcTwo` subroutine is partially implemented due to the presence of the `print` statement. The `...` statements in lines $9$ and $10$ serve as placeholders for the unimplemented statements of `funcTwo`.

Perl parses the `...` statements in the subroutines and the `eval` statement without any errors; however, an `Unimplemented` exception is thrown when the `funcOne` and `funcTwo` subroutines are invoked in lines $17$ and $22$, respectively.

<h3>Syntax errors</h3>

Ellipsis statements cannot be used as placeholders for expressions in larger statements, e.g., `if-else` statements or mathematical operations. The invalid usage of the ellipsis statement results in a syntax error.

The snippet below shows how syntax errors may arise from the use of the ellipsis statement:

```Perl

## Placeholder for expression in if-condition
if( $condition && ...){ print "OK"};

## Placeholder for part of mathematical expression
$sum = 5 + ...;

```



What is the ellipsis statement in Perl?

Perl's ellipsis statement ( ... ) acts as a placeholder for unimplemented code, causing an Unimplemented exception if executed.