Powershell script to replace a section of url in a particular field of an item in sharepoint List

try the following command:

Add-PSSnapin Microsoft.SharePoint.PowerShell

#Variables that we are going to use for list editing

$webURL = <a href="http://ift.tt/162wJMV; http://ift.tt/1JRLLmL </a>

#Get the SPWeb object and save it to a variable

$web = Get-SPWeb $webURL

#Get the SPList object to retrieve the "Demo List"

$list = $web.Lists[$listName]

#Get all items in this list and save them to a variable

$items = $list.items

#Go through all items

foreach($item in $items)

{

if($item["UrlColumn"] -eq "http://ift.tt/162wK3d;)

{

#Change the value of the "Title" column

$item["UrlColumn "] = " http://test.com/abc=123 "

#Update the item

$item.Update()

}

}
In case of issues check 
http://ift.tt/1JRLLmN

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